1. Field of the Invention
The present invention relates to an electrocurtain coating process for coating solar mirrors, and more particularly, to a method of depositing an electrodepositable coating composition, e.g. an electrodepositable protective coating over the reflective coating of solar mirrors through the use of a plurality of electrically conductive liquid streams.
2. Discussion of the Presently Available Technology
In general, solar mirrors include a transparent substrate, e.g. a glass substrate having a solar reflective coating on a surface of the glass substrate facing away from the sun. A coating is applied over the surface of the reflective coating exposed to the environment to protect the reflective coating against chemical attack, e.g. against oxidation and/or corrosion caused by rain and chemicals in the environment, and against mechanical damage, e.g. scratches and impact abrasion. As is known there are different techniques to apply a protective coating over a surface to protect the surface against chemical and mechanical damage. One coating technique of particular interest is the process to deposit an electrodepositable coating composition onto a surface. In this process, an electrodepositable coating, which is also referred to as an “e-coat” or electrodeposition coating composition, is deposited onto a conductive surface of a substrate using an electrical process.
In general, the e-coat coating process can be seen as an electrical circuit when an electrical current is applied to the system. In this electrical circuit, the electrodepositable coating composition has a cationic or anionic charge while the electrically conductive surface of the substrate, which is to be coated, has a charge that is opposite to that of the electrodepositable coating composition, i.e., the electrically conductive surface of the substrate can be anionic or cationic, respectively. During the coating process, a complete electrical circuit is established by a direct current rectifier thereby allowing the coating composition to deposit onto the oppositely charged conductive surface of the substrate. However, in order to complete the electrical circuit, the electrically conductive surface of the substrate is grounded or connected to the rectifier through the use of a mechanical contact, such as a clip, which contacts or is connected to the conductive surface of the substrate.
A limitation of using a mechanical contact, however, is that the point or area of contact (“contact area”) will not be coated with the electrodepositable coating composition because it is covered by the contact surface of the mechanical contact and, therefore, the electrodepositable coating composition is not applied to the contact area. Since the contact area is not coated with the electrodepositable coating composition, the coating void not only detracts from the visual appearance of the solar mirror (i.e., the outer surface of the reflective coating is not uniformly coated with the electrodepositable coating composition), the coating void is also more susceptible to chemical attack when compared to an area that has been coated with the electrodepositable protective coating composition.
As can be appreciated by those skilled in the art, it would be advantageous to provide a method of depositing an electrodepositable protective coating composition on the reflective surface of a solar mirror while eliminating the mechanical contact.